Taking to the skies
The mammals that we have studied so far, almost all feed on invertebrates, particularly insects, however a large number of insects fly and therefore are able to escape such predators. Insects first took to the air some 300 million years ago and had the skies to themselves until the arrival of the flying reptiles like the pterosaurs, some hundred million years later. Whether the reptiles flew at night is not known although unlikely bearing in mind the reptilian problem of maintaining body temperature. Birds eventually succeeded them, but there is no reason to suppose than there were any more night flying birds in the past than there are today which is very few. Consequently the night skies offer the best refuge from predation until another variation on the insectivore theme evolved: the bats.